Humans and animals with deficient ataxia telangiectasia mutated (ATM) are insulin-resistant or hyperglycemic. ATM reportedly indirectly influences insulin signaling, including phosphorylation of Akt, in various cell types. There is also evidence that ATM is an activating kinase for the AMP-activated protein kinase (AMPK), a mediator of insulin-independent stimulation of glucose transport. However, the potential roles of ATM in AMPK- and insulin-stimulated glucose transport have not previously been addressed in skeletal muscle, the predominant tissue in insulin-stimulated glucose disposal. Preliminary data from cultured myotubes demonstrate that a specific ATM inhibitor prevents stimulation of glucose transport by insulin and the AMPK activator AICAR. The specific aims are: 1) to test the hypothesis that ATM plays a role in insulin-independent stimulation of glucose transport by AMPK-activating treatments (e.g. exercise and/or the AMPK activator AICAR) in skeletal muscle, 2) to test the hypothesis that ATM plays a role in insulin-stimulated glucose transport and insulin signaling in skeletal muscle, and 3) to test the hypothesis that ATM directly phosphorylates and/or alters activity of components of the insulin signaling pathway in skeletal muscle. Experimental tools will include ATM deficient transgenic mice, a specific inhibitor of ATM, and an antibody specific for proteins that have been phosphorylated by ATM. Elucidating the possible role of a factor like ATM that might play a role in regulation of glucose transport stimulated by either AMPK or insulin--or both--is potentially valuable to describing new approaches to prevention or treatment of diabetes. PUBLIC HEALTH RELEVANCE STATEMENT: The project will examine the potential role of a protein called ATM in regulation of sugar transport into muscle in response to exercise and insulin, a hormone that enters the bloodstream when blood sugar levels increase. Understanding the factors that cause muscles to clear sugar from the bloodstream is vital to developing strategies to treat or prevent the high blood sugar concentrations that are the hallmark of diabetes.